Caps for providing air-tight or water-tight seals over openings in containers and pipes are known in the art. Many of these devices are cumbersome to operate in that they require multiple turns of a handle or enough applied force to compress a spring to achieve closure. Further repeated opening and closing of the cap leads to undesirable wear of the seal, because the turning of the handle causes the seal to turn relative to the opening of the container.
A sealing cap for a gasoline tank is disclosed with a sealing ring for sealing a filler neck of the gasoline tank (U.S. Pat. No. 4,436,219). The sealing ring is attached to a lower shoulder portion of the sealing cap. A spring is disposed between the lower shoulder portion and a turning stop. When the sealing cap is inserted into the filler neck and rotated, the turning stop of the sealing cap engages tabs on the interior of the filler neck preventing further rotation of the turning stop and those parts non-rotatably engaged thereto. Subsequent rotation of the sealing cap compresses the spring disposed between the turning stop and the lower shoulder portion seating the sealing ring against the filler neck.
A cap is desired which achieves a sealed closure with only a one quarter turn in rotation without rotating the seal relative to the sealing surface of an opening of a container to prevent excessive seal wear. In addition, a cap is desired which achieves a seal closure under the force of an expanding spring upon rotation of the handle to eliminate the necessity of applying a compressive force to the spring to achieve closure.